The idea of the existence of ether has been abandoned after the theory of relativity was accepted. It appears that the existence of an ether, compatible with the classical standard Cosmological model, permits to solve some enigmas of the present Cosmological model that are very important, for instance the enigma connected to dark matter or to fossil radiation. In this article we show how the existence of ether, being compatible with the classical standard Cosmological model, permits to solve those enigmas. In particular how it can give the nature of dark matter, the origin of its invisibility, the curve of velocities of stars in galaxies (constant) and the baryonic Tully-Fisherâs law.